Salicornia, also known as Samphire, Prickelweed or Sea Bean, is native to most shorelines at our Atlantic and Pacific Coasts. Walking along a marsh you probably stepped on it, but didn’t pay attention. It is great with seafood dishes, in Paris it is sold by fishmongers, in the US you rarely find it.
It can be foraged, make sure you are not on a protected beach and don’t take the entire plant, clip the parts you want to eat and let it grow back.
Salicornia grows in the tidal zone and is completely tolerant to salt water, which minimizes competition from other plants and weeds. It is not a seaweed, botanically speaking it is a succulent. In many places it gets submerged by the incoming tide and depending on the salinity of the ocean it can get really salty. Clip the young sprouts; the older growth is too coarse.
It can also be homegrown, native plant nurseries typically carry it. If you grow it home you can adjust the saltiness by feeding it water with sea salt, or just water; the plant will extract salt from the soil and store it in its sprouts, bursting with flavor.
It can be eaten just raw, sprinkled over seafood, or blanched and eaten like vegetable and it also freezes well.